This invention relates to apparatus for extinguishing a fire in a storage tank. More particularly, this invention relates to a fire extinguishing mechanism movably coupled to the lip of an oil storage tank so that the apparatus can move around the storage tank lip to an appropriate location to direct fire suppressant material on the fire.
With the increasing use of petrochemical substances in our society, petrochemical storage tanks are being located in a wide variety of work locations, such as tank "farms", factories, process plants, refineries, etc. Fire hazards associated with such storage tanks are well known and must be adequately addressed before the tanks can be properly positioned in any work environment. In large storage tank farms, the fire hazard is exacerbated by the great number of tanks requiring fire detection/suppression, and the possibility of fire being transmitted from one tank to the next. Therefore, it is essential that apparatus be provided which is capable of quickly and efficiently suppressing a fire ignited on the inside of a petrochemical storage tank.
The typical petrochemical storage tank is cylindrical in shape and has a roof which floats on the petrochemical stored within the tank. The floating roof includes flexible seals at its periphery to movably seal the floating roof to the inside of the storage tank. It is at this periphery that the greatest danger of fire exists. Fires in such floating roof tanks is usually ignited and sustained at the gap between the floating roof periphery and the interior wall of the tank. It is therefore essential to quickly and efficiently place fire suppressant materials around the interior surface of the petrochemical storage tank.
Many fire suppression systems are known which actively suppress a fire in a floating roof oil storage tank. U.S. Pat. No. 3,896,881 to De Boer discloses an automatic fire extinguisher having a fluid distribution pipe network extending around the periphery of the floating roof. This pipe network carries fire extinguisher materials around the periphery of the floating roof. A plurality of fire extinguisher storage tanks are coupled to the pipe distribution network at various locations around the floating roof. The pipe distribution network includes a plurality of sprinklers which direct the fire suppressant material to the gap between the floating roof and the inside wall of the storage tank. Each sprinkler is designed to open at a given temperature so that the system automatically detects and responds to a fire inside the storage tank. De Boer even proposes a second pipe distribution network having sprinklers which operate at a different temperature than the sprinklers of the first network. Thus, fires of different intensities may be fought with this apparatus.
However, the distributed sprinkler apparatus according to De Boer is incapable of providing a large quantity of fire suppressant material directly onto a fire. Each sprinkler of De Boer is only capable of providing a fixed amount of fire suppressant material at a given location. If the fire is very intense at a specific location, it is possible that insufficient fire suppressant material will be provided to extinguish the blaze. In addition, the apparatus according to De Boer is adapted to be permanently fixed to the floating roof inside the storage tank. This greatly adds to the time and expense necessary to manufacture these floating roofs. Existing storage tank roofs would have to be extensively modified to practice the invention according to the apparatus of De Boer. Finally, the De Boer apparatus cannot be moved from tank to tank in response to fire conditions. Thus, the cost of each storage tank is greatly increased and the majority of the De Boer apparatuses will never be used since the majority of oil storage tanks never catch fire.
U.S. Pat. No. 1,955,265 to Warnock solves some of the above-discussed problems by providing a foam applicator capable of being moved from tank to tank in response to a given fire condition. As depicted in FIG. 1, the apparatus according to Warnock provides apparatus used to hoist the foam nozzle over the lip of the oil storage tank. Hook 3 is coupled to the lip of the storage tank while block and tackle 22, 23, and 24 are manipulated to hoist foam nozzle 21 over the lip of the tank. However, as can be appreciated from FIG. 5, once the foam nozzle has been positioned it is very difficult to move the foam nozzle around the lip of the tank. Thus, where the fire has been suppressed at one portion of the storage tank, the Warnock apparatus requires a difficult and time consuming effort to move the nozzle to another location on the tank. While the nozzle is being moved, it is entirely probably that the fire will be reignited in the already-extinguished portions of the tank.
Therefore, it is apparent that what is needed is a storage tank fire-suppression apparatus which is capable of being inexpensively manufactured, easily transported to the storage tank, and coupled to the storage tank in such a way as to enable the fire suppressant material to be quickly applied directly at the location of the fire. Such an apparatus should be movable around the tank so that fire extinguishing materials may be quickly and accurately directed to the fire source.